Topic 2: Bonding and Structure

Question 1

What is ionic bonding?

Answer 1

Ionic bonding is the strong electrostatic forces of attraction between oppositely charged ions (metal + non-metal)

Question 2

How does an ion form?

Answer 2

An ion forms when an atom loses or gains electrons

Question 3

How can ionic radius affect the strength of ionic bonding

Answer 3

Smaller ions can be packed more closely together in the ionic lattice, resulting in stronger bonds. Larger ions have a weaker attraction to oppositely charged ions because the attractive forces have to act over a greater distance.

Question 4

How can ionic charge affect the strength of ionic bonding?

Answer 4

Ions with a greater charge have a greater attraction to other ions, resulting in stronger ionic bonding. For example, an aluminum ion with a charge of three plus will form a stronger ionic bond with a chloride ion than a sodium ion with a charge of one plus.

Question 5

How can charge density affect the strength of ionic bonding?

Answer 5

As the ionic charge increases, or the ionic radius decreases, the charge density increases, which results in stronger bonds.

Question 6

What happens to ionic radii down a group?

Answer 6

Ionic radii increase as you move down a group on the periodic table. As you move down a group, each element has an additional electron shell. This increases the distance between the nucleus and the outer electrons, reducing the attractive force. The inner shells also create a barrier that blocks the attractive forces, further reducing the nuclear attraction.

Question 7

What happens to ionic radii across a group?

Answer 7

Ionic radii decreases because the number of protons in the nucleus increases. This pulls the electrons more tightly towards the nucleus, decreasing the ionic radius.

Question 8

The trend of ionic radii with isoelectronic ions

Answer 8

The ionic radius of isoelectronic ions decreases as the number of protons in the nucleus increases.
Isoelectronic ions have the same number of electrons, but the size of the ion is determined by the charge on the nucleus. When the number of protons in the nucleus increases, the electrons are pulled closer to the nucleus, which decreases the ionic radius.

Question 9

Physical properties of ions

Answer 9

Substances with ionic bonding have a high melting point and boiling point. This is because of strong electrostatic forces of attraction requires lots of energy to overcome. When molten or dissolved in solution, ionic substances can conduct electricity. In this state, the ions separate and are no longer in a lattice meaning they are free to move and carry charge. Ionic substances are brittle (brittle material).

Question 10

What is a covalent bond?

Answer 10

Strong electrostatic forces of attraction between two nuclei and the shared pair of electrons between them (non-metal + non-metal)

Question 11

How do bond lengths affect a covalent bond strength?

Answer 11

Bond length is the average distance between two nuclei in a covalent bond with the shorter bonds being stronger. The distance between the nuclei of two covalently bonded atoms is the bond length. When atoms are closer together, the forces of attraction are greater, making the bond stronger. Triple bonds are the shortest and strongest covalent bonds, followed by double bonds, and then single bonds. The large electron density between the nuclei of two atoms in a triple bond increases the forces of attraction between the electrons and nuclei.

Question 12

How is a shape of an ion determined?

Answer 12

Repulsion between the electron pairs that surround a central atom

Question 13

Different shapes and angles of molecules and ions

Answer 13

Linear (2 bonding pairs and no lone pairs) = 180 degrees
V-Shaped (2 bonding pairs and 2 lone electron pairs) = 104.5 degrees
Trigonal Planar (3 bonding pairs and no lone electron pairs) = 120 degrees
Triangular Pyramid (3 bonding pairs and 1 lone electron pairs) = 107 degrees
Tetrahedral (4 bonding pairs and no lone electron pairs) = 109.5 degrees
Trigonal Bipyramidal (5 bonding pairs and no lone electron pairs) = 90-120 degrees
Octahedral (6 bonding pairs and no lone electron pairs) = 90 degrees

Question 14

What is electronegativity?

Answer 14

Electronegativity is the ability of an atom to attract the bonding electrons in a covalent bond

Question 15

Are ionic and covalent bonding extremes of a continuum bonding? State reasons.

Answer 15

Yes, ionic and covalent bonding are the extremes of a continuum of bonding types.
Ionic bonding: Occurs when one or more electrons are removed from one atom and attached to another, creating positive and negative ions that attract each other.
Covalent bonding: Occurs when one or more pairs of electrons are shared between two atoms.

Question 16

How to determine the type of bonds a molecule forms using electronegativity?

Answer 16

Greater electronegativity difference: Results in a greater ionic character of the bond.
More similar electronegativities: Results in a greater covalent character of the bond.

Question 17

Are molecules with polar bonds polar molecules?

Answer 17

No. A molecule with polar bonds may or may not be polar, depending on the molecule’s geometry and the distribution of charge.
Polar molecules A molecule is polar if it has one or more polar bonds and the dipoles created by those bonds don’t cancel each other out. For example, water is polar because its bent geometry means the dipoles created by the polar (O-H) bonds don’t cancel each other out. Non-polar molecules A molecule is non-polar if the dipoles created by its polar bonds cancel each other out. For example, carbon dioxide is non-polar because its linear geometry means the dipoles created by the polar (C=O) bonds cancel each other out.

Question 18

Name the intermolecular forces

Answer 18

London forces
Permanent dipoles
Hydrogen bonds

Question 19

How does Hydrogen bonding occur?

Answer 19

Hydrogen bonds only act between hydrogen and the three most electronegative atoms:​ nitrogen, oxygen and fluorine​. The ​lone pair​on these atoms form a bond with a + hydrogen atom from another molecule, δ shown with a ​dotted line​.

Question 20

How does water have a relatively high melting and boiling point?

Answer 20

Water has high melting and boiling points because of the strong hydrogen bonds between water molecules.
Hydrogen bonds are the strongest type of intermolecular force. They only occur between hydrogen and the three most electronegative atoms: nitrogen, oxygen, and fluorine.
A large amount of energy is needed to break the hydrogen bonds between water molecules, which is why water has a high melting and boiling point.
Hydrogen bonds create a rigid structure
Hydrogen bonds hold water molecules in a rigid structure with lots of air gaps, which is why ice has a lower density than liquid water.

Question 21

Compare the density of ice in comparison to water

Answer 21

Ice is less dense than water because the hydrogen bond orientation in ice causes the molecules to push farther apart, lowering the density.

Question 22

Explain the trends in boiling temperatures of alkanes with increasing chain length

Answer 22

The boiling point of alkanes increases as the length of their carbon chain increases. Longer chains have more points of contact, which results in stronger intermolecular forces. This means that the liquid needs to reach a higher temperature before the molecules can separate and turn into vapor.

Question 23

Explain the effect of branching in the carbon chain on the boiling temperatures of alkanes

Answer 23

Branched-chain alkanes have lower boiling points than straight-chain alkanes. This is because branching reduces the surface area of contact between molecules, which weakens the van der Waals attractions.

Question 24

Explain the relatively low volatility of alcohols compared to alkanes with a similar number of electrons

Answer 24

Alcohols have a lower volatility than alkanes with a similar number of electrons because alcohols have stronger intermolecular forces between their molecules.
Alcohols have hydrogen bonds between their molecules, which are stronger than the van der Waals forces between alkanes.
More energy is required to break the hydrogen bonds in alcohols than the van der Waals forces in alkanes, so alcohols have higher boiling points than alkanes.

Question 25

Explain the trends in boiling temperatures of the hydrogen halides HF to HI

Answer 25

The boiling point ​increases​as you move down the group past hydrogen fluoride because as the halide increases in size, their ​number of electrons ​also increases. This means more​ van der waals​ forces form between molecules, so more energy is required to separate them.

Question 26

Explain the factors that influence the choice of solvents (Water) to dissolve some ionic compounds

Answer 26

Many ionic compounds dissolve in polar solvents, like water, because the polar molecules can break down the ionic lattice and surround the ions. The δ+ end of the polar molecule surrounds the negative anion, and the δ- end surrounds the positive cation.

Question 27

Explain the factors that influence the choice of solvents (Water) to dissolve simple alcohols

Answer 27

Water can dissolve simple alcohols. Alcohols are compounds with a hydroxyl group and as a result can form hydrogen bonds with water. However, long chain alcohols are less soluble in water because more bonds have to be broken down than those that get formed. As a result, energy released from bond formation does not compensate for the energy lost during bond breakage so that the alcohol dissolves poorly in water.

Question 28

Explain the factors that influence the choice of solvents (Water) as a poor solvent for polar compounds as they cannot form hydrogen bonds

Answer 28

Water is a poor solvent for some polar compounds because they cannot form hydrogen bonds with water molecules:
Hydrogen bonds are stronger than dipole interactions.
The hydrogen bonds between water molecules are stronger than the dipole interactions that can form between water molecules and some polar compounds.
Some polar compounds, like halogenoalkanes, have a dipole moment that is too weak to form hydrogen bonds with water molecules.
Non-polar compounds are insoluble: Non-polar compounds, like iodine, are completely insoluble in water.

Question 29

What is metallic bonding?

Answer 29

Strong electrostatic forces of attraction between metal ions and delocalised electrons

Question 30

What are giant lattices present in?

Answer 30

Ionic solids (giant ionic lattice)
Covalently bonded solids like diamond and graphite (giant covalent lattice)
Solid metals (giant metallic lattices)

Question 31

What is the structure of covalently bonded substances (like iodine and ice)

Answer 31

Simple molecular

Question 32

Name 3 different carbon structures

Answer 32

Graphite
Graphene
Diamonds

Question 33

How to predict the type of structure based on numerical data and other information

Answer 33

Using the data booklet to interpret different values of different molecules and then calculating by finding Mr

Question 34

How to predict the physical properties of a substance with the structure?

Answer 34

The type of structure a compound has will determine its physical properties. For example, a giant ionic structure has a high melting point, is soluble in water, and conducts electricity when molten. A simple molecular structure has a low melting point, is almost insoluble in water, and has low electrical conductivity.

Question 35

How to predict the physical properties of a substance with the type of bonding and the presence of intermolecular bonds?

Answer 35

The strength of the intermolecular forces between molecules determines a compound’s physical properties, such as melting and boiling points. Stronger intermolecular forces require more energy to break, resulting in higher melting and boiling points. Ionic and metallic bonding typically